I might be able to shed some light on the Lightspeed question, if only by extrapolation. Like Whart, I prefer the Steelhead into a preamp. Directly into my amps (whether Bryston 28b-SST2 or Reference Line Silver Signature), I found it to be nicely transparent and dynamic but also to collapse the soundstage vertically somewhat and take on a bit of an edge. Running it into a Bent TAP-X passive that uses autoformers, however, all of the transparency and dynamics are retained but the soundstage is expanded to its realistic proportions. It sounds fuller and more natural. The AVC TAP-X has been compared to the Lightspeed sonically, so I'd guess something similar would happen with the latter.
As a linestage, the Steelhead wasn't as threadbare in my system as Whart describes, perhaps because I use a different, fatter-sounding tube compliment: Valvo Red Label 6922, plus Amperex 7119 and GE 7044 in place of the two pairs of stock 5687. The 7044 is richer than any of the 5687 I've tried, and the 7119 is richer still. These work best for me, but I'm using solid state amps. The best sound in my system is into a VAC Phi Beta tube preamp.
As a linestage, the Steelhead wasn't as threadbare in my system as Whart describes, perhaps because I use a different, fatter-sounding tube compliment: Valvo Red Label 6922, plus Amperex 7119 and GE 7044 in place of the two pairs of stock 5687. The 7044 is richer than any of the 5687 I've tried, and the 7119 is richer still. These work best for me, but I'm using solid state amps. The best sound in my system is into a VAC Phi Beta tube preamp.